This project concerns the development of technology to streamline the ability to manipulate stem cells in culture and automate the acquisition of information from these cells. A system is proposed that uses microfabrication--the same technology used to make computer chips--to make large arrays of small chambers in which one can grow stem cells. The culture conditions in each of these chambers can be varied, allowing one to perform many experiments simultaneously. In addition, single cells will be positioned in these chambers using electric fields, allowing for a significant increase in the density of stem cell colonies, and thus a higher number of chambers on each chip. This microsystem will have environmental control of the chambers (temperature, pH, oxygen) and will couple to an automated microscopy system to allow for in situ analysis of cell phenotype. The complete system will have a small form factor (the size of a glass slide) and be inexpensive enough to be widely accessible. Initial studies will be performed examining the role of autocrine signaling on the maintenance of mouse embryonic stem cell phenotype, using the microfluidics to precisely deliver varying concentrations and flow rates of cytokines to the cell colonies.